Related Clues:

• Attack ad, maybe
• Slide specimen
• Malign
• Besmirch
• Slight on the stump, say
• Drag through the mud
• Mirror marrer
• Campaign low blow
• Underhanded campaign tactic
• Bad mark
• Window washer's mistake
• Fingerpaint
• Microscope sample
• Makeup problem
• Sling mud at, politically